1. Technical Field
The present invention relates to a receiver for estimation or compensation of phase imbalance or gain imbalance and methods which can be applied in a receiver for estimation or compensation of phase imbalance or gain imbalance. A transmission technique used in the receiver is based on a QPSK (quadrature phase shift keying) modulation and a modulation scheme based on complex scrambling code.
2. Description of the Related Art
The Universal Mobile Telecommunications System or UMTS is one of the major new ‘third generation’ (3G) mobile communications systems being developed within the framework defined by the ITU (International Telecommunication Union) and known as IMT-2000.
Methods for estimation or compensation of phase imbalance or gain imbalance typically rely on reference signal generation, adaptive interference cancellation, blind source separation or a least square approach in the Fourier domain. Such methods are known, e.g., from “Digital I/Q imbalance compensation in a low-if receiver”, Jack P. Glas (Bell Labs)-1998-IEEE, “Improving QPSK Demodulator Performance for Quadrature Receiver with Information from Amplitude and Phase Imbalance Correction”, Hung Ngyen (The Aerospace Corp.)-2000-IEEE, “Blind Source Separation Based I/Q imbalance compensation”, Valkama, Renfors, Koivunen-2000-IEEE, “Advanced methods for I/Q imbalance compensation in Communication Receivers”, M. Valkama, M. Renfros, V. Koivunen-IEEE transactions on signal processing-Vol. 49, no. 10, October 2001.
WO 0150616 discloses a receiver for correcting the phase error in a received signal. However, this receiver does not provide an efficient estimation or compensation of phase imbalance or gain imbalance in the received signal.